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THE NEW YORKER, APRIL 22, 2013
is happiest in situations like this: sur-
rounded by whiteboards and brilliant
minds, brainstorming ideas and win-
nowing them down. His house in Al-
tadena, a modest bungalow surrounded
by exotic fruit trees that he and his wife
planted, often serves as a late-night de-
sign-and-disputation forum, with a full
bar in the living room. (When I visited
on the day of the Curiosity landing, the
mirror above the mantel was covered in
half-erased equations.) The session at
J.P.L. went on for three days, then recon-
vened two weeks later, to make sure that
everybody hadn't gone crazy. "The man-
ager guys were literally squirming in their
seats," Rivellini said. "They kept trying to
guide the conversation back to legged
landers, but we just didn't want any of it."
What they did want was "Rover on a
Rope." This was an idea first floated for
the sample-return mission. It involved
lowering the rover to the ground on ca-
bles while the landing shell was still at-
tached to its parachute. The concept had
been deemed too hard to control: the
rover would swing like a pendulum as it
flew, and its radar was too inaccurate to
find safe anchorage. But that was then,
Miguel San Martín said. His guidance-
and-navigation team had reëngineered
the thrusters to make the lander more
maneuverable. Its radar was much im-
proved, and the new software they'd pro-
grammed could stabilize anything swing-
ing beneath it. "It was one of those 'Aha!'
moments," Rivellini recalls. "The whole
team just got it." (The final patent would
have nine names on it, Steltzner says, but
it could have had many more.) If the
guidance system was that good, why not
get rid of the parachute earlier, and jetti-
son the landing shell? That would leave a
small, mobile craft that could maneuver
on thrusters alone, hover near the surface,
and lower the rover down. "With just a
little bit of extra work," Rivellini said, "we
can get rid of the air bags and land this
thing right on its wheels."
The Sky Crane, as the new lander was
called, turned NASA's previous design
philosophy on its head. It swapped a sim-
ple, sloppy, but proven technology (air
bags) for a complex, precise, and un-
proven one. "We wanted an all-access
pass to Mars," Steltzner told me. Since
the lander was now much more maneu-
verable, it could target a much smaller
area---around fifty square miles---and
avoid most obstacles within it. It could
land big rovers or small, on flat terrain or
sloped, in all kinds of weather. But only
if everything worked---if the cables didn't
jam or the thrusters misfire or the radar
malfunction or the rocket engine ex-
plode. For every one thing that could go
wrong with air bags, the Sky Crane had
a thousand. "The thing I'm most scared
about is the thing I don't know," Steltz-
ner told me. "Where does it live? It lives
in the complexity of the beast that we've
created---in the gremlin of self-generated
complexity."
At J.P.L. one afternoon, Steltzner
showed me a scale model of the final de-
sign, with its spidery legs. Built by a man
named Hirai Isao, who makes most of
NASA's models, it looked and felt like a
high-end Star Wars toy (cost: five thou-
sand dollars); a smaller version was al-
ready licensed for mass production. "You
can just imagine what they could do with
it," Steltzner said, playing with its cables
and tiny articulations. "It could have
these beautiful die-cast parts, and little
L.E.D.s where the thrusters are." He was
careful to speak in the conditional: there
was once a toy Polar Lander, too, but
Mattel stopped making it when the mis-
sion failed. "The rover is called Curios-
ity," he said, "but we secretly named the
descent stage Audacity."
The morning of the landing dawned
bright and clear in Southern Cali-
fornia, as it did on the next planet over.
"It's a fine Martian day," Doug McCuis-
tion, the Mars program director, de-
clared. "The sun's coming up at Gale
Crater. It's gonna be warm. It's gonna be
sunny." He grinned at the cameramen
clustered around the lectern, the jour-
nalists now gathered in force in J.P.L.'s
von Kármán Auditorium, with satellite
vans parked outside. "This is it: the
Super Bowl of planetary exploration.
One yard left."
McCuistion's weather report was
more than just scene setting. Curiosity
was landing on Mars in an uneasy season,
when the planet was swinging closer to
the sun on its eccentric orbit, stirring up
an already volatile climate. Compared
with the sluggish air on Earth, the Mar-
tian atmosphere is in constant motion:
between the surface and six feet above it,
temperatures can vary by as much as sixty
degrees. The air is so thin that the first
glimmer of sun can throw it into violent
convection, lofting up into towering
thermals, twisting into dust devils, and
collapsing back down as they cool. Any
loose dust picked up along the way will
absorb still more heat, creating a feed-
back loop that can send storms surging
across the face of the planet.
NASA keeps a set of sharp eyes on
these developments through Odyssey
and the Mars Reconnaissance Orbiter,
and more than a dozen climate special-
ists who sift through the data they send
back. (One of them, Bruce Cantor, of
Malin Space Science Systems, in San
Diego, has spent fourteen years tracking
every dust storm on the planet.) Using
The work of seven thousand people,